DEBT AND OTHER OBLIGATIONS - Repurchase Agreements (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Repurchase agreements and repurchase-to-maturity transactions	$ 451,895	$ 1,006,607
Securities lending transactions	72,176	125,271
Total securities	524,071	1,131,878
U.S. government-related securities
Debt Instrument [Line Items]
Repurchase agreements and repurchase-to-maturity transactions	451,895	307,633
Mortgage loans
Debt Instrument [Line Items]
Repurchase agreements and repurchase-to-maturity transactions	0	698,974
Corporate securities
Debt Instrument [Line Items]
Securities lending transactions	71,285	118,817
Equity securities
Debt Instrument [Line Items]
Securities lending transactions	891	5,699
Redeemable preferred stock
Debt Instrument [Line Items]
Securities lending transactions	0	755
Overnight and Continuous
Debt Instrument [Line Items]
Repurchase agreements and repurchase-to-maturity transactions	433,182	1,006,607
Securities lending transactions	72,176	125,271
Total securities	505,358	1,131,878
Overnight and Continuous \| U.S. government-related securities
Debt Instrument [Line Items]
Repurchase agreements and repurchase-to-maturity transactions	433,182	307,633
Overnight and Continuous \| Mortgage loans
Debt Instrument [Line Items]
Repurchase agreements and repurchase-to-maturity transactions	0	698,974
Overnight and Continuous \| Corporate securities
Debt Instrument [Line Items]
Securities lending transactions	71,285	118,817
Overnight and Continuous \| Equity securities
Debt Instrument [Line Items]
Securities lending transactions	891	5,699
Overnight and Continuous \| Redeemable preferred stock
Debt Instrument [Line Items]
Securities lending transactions	0	755
Up to 30 days
Debt Instrument [Line Items]
Repurchase agreements and repurchase-to-maturity transactions	18,713	0
Securities lending transactions	0	0
Total securities	18,713	0
Up to 30 days \| U.S. government-related securities
Debt Instrument [Line Items]
Repurchase agreements and repurchase-to-maturity transactions	18,713	0
Up to 30 days \| Mortgage loans
Debt Instrument [Line Items]
Repurchase agreements and repurchase-to-maturity transactions	0	0
Up to 30 days \| Corporate securities
Debt Instrument [Line Items]
Securities lending transactions	0	0
Up to 30 days \| Equity securities
Debt Instrument [Line Items]
Securities lending transactions	0	0
Up to 30 days \| Redeemable preferred stock
Debt Instrument [Line Items]
Securities lending transactions	0	0
30 - 90 days
Debt Instrument [Line Items]
Repurchase agreements and repurchase-to-maturity transactions	0	0
Securities lending transactions	0	0
Total securities	0	0
30 - 90 days \| U.S. government-related securities
Debt Instrument [Line Items]
Repurchase agreements and repurchase-to-maturity transactions	0	0
30 - 90 days \| Mortgage loans
Debt Instrument [Line Items]
Repurchase agreements and repurchase-to-maturity transactions	0	0
30 - 90 days \| Corporate securities
Debt Instrument [Line Items]
Securities lending transactions	0	0
30 - 90 days \| Equity securities
Debt Instrument [Line Items]
Securities lending transactions	0	0
30 - 90 days \| Redeemable preferred stock
Debt Instrument [Line Items]
Securities lending transactions	0	0
Greater Than 90 days
Debt Instrument [Line Items]
Repurchase agreements and repurchase-to-maturity transactions	0	0
Securities lending transactions	0	0
Total securities	0	0
Greater Than 90 days \| U.S. government-related securities
Debt Instrument [Line Items]
Repurchase agreements and repurchase-to-maturity transactions	0	0
Greater Than 90 days \| Mortgage loans
Debt Instrument [Line Items]
Repurchase agreements and repurchase-to-maturity transactions	0	0
Greater Than 90 days \| Corporate securities
Debt Instrument [Line Items]
Securities lending transactions	0	0
Greater Than 90 days \| Equity securities
Debt Instrument [Line Items]
Securities lending transactions	0	0
Greater Than 90 days \| Redeemable preferred stock
Debt Instrument [Line Items]
Securities lending transactions	$ 0	$ 0

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No definition available.

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- Definition

Amount, before effects of master netting arrangements, of funds outstanding borrowed in the form of a financial asset repurchase agreement between the entity and another party for the sale and repurchase of identical or substantially the same financial asset at a date certain for a specified price. Includes repurchase-to-maturity transactions and liabilities not subject to a master netting arrangement.

+ References

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- Definition

Amount, before effects of master netting arrangements, of financial assets loaned to entities in exchange for collateral and funds outstanding borrowed in the form of a financial asset repurchase agreement between the entity and another party for the sale and repurchase of identical or substantially the same financial assets at a date certain for a specified price. Includes liabilities not subject to a master netting arrangement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 50
-Paragraph 7
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109249958&loc=SL34722452-111729

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 50
-Paragraph 7
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=109249958&loc=SL34722452-111729

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- Definition

Amount, before effects of master netting arrangements, of financial assets loaned to entities in exchange for collateral. Includes liabilities not subject to a master netting arrangement and financial assets transferred other than securities that qualify as secured borrowings.

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